Process for manufacturing gasoline by distillation



April 6, 1937. u 2,076,214

` l J. H. w. RosT VAN TONNINGEN PROCESS FOR MANUFACTURING 4GASOLINE BY DISTILLATION Filed Oct. 29, 1934 Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE PROCESS FOR MANUFACTURING GASOLINE BY DISTILLATION Application October 29, 1934, Serial No. 750,545 In the Netherlands November 8, 1933 2 Claims.

My invention relates to a process for manufacturing gasoline by distillation of hydrocarbon mixtures containing gasoline such as crude petroleum an-d crude petroleum distillates.

5 The object of my invention is to carry out the distillation in such a manner as to obtain a gasoline of the highest possible antiknock value (highest useful compression).

It is already known that in general the highest useful compression ratio (H. U. C.) of light motor fuels produced from crude petroleum increases with their volatility. This makes it desirable to produce gasolines with the greatest possible quantity of volatile hydrocarbons.

However, a limit is put on this quantity first because the gasoline must be stable, that is to say, it must not contain any wholly or partially gaseous components such as propane and possibly butane, and second because one has to take into account a certain production of gasoline,

that is to say that when meeting a special requirement in the way of a great volatility it would perhaps be impossible to produce such a gasoline from a given base material in sufficient quantities. It is therefore essential to be as eco nomical as possible with the volatile hydrocarbons, more particularly to take care that no suiiiciently volatile constituents suitable to be used as gasoline get into the next higher fraction as a result of an insufficiently sharp fractionation. Moreover an ineflicient fractionation causes a transfer to the gasoline of insufficiently volatile constituents which actually belong to the next higher fraction, thus adversely aiecting the antiknock value. On examining the correlation between the volatilityby which is meant here the volume percentage of a hydrocarbon mixture distilling over up to 100 C., to be determine-d according to the A. S. T. M. method-and the antiknock properties-for which the H. U. C. was taken as a measureit was unexpectedly found that in the case of gasolines obtained from petroleums of dilerent origin the H. U. C., which gradually decreases with a decrease of volatility, 4 at a certain degree of volatility or at a certain boiling point, shows a much stronger tendency to decrease than before.

This phenomenon is illustrated in the appended graph. Of three crude oils A, J. and P, with asphalt base, mixed base and paraffin base respectively, the curve was plotted indicating the relation between the H. U. C. and the volatility. The H. U. C. is set out on the vertical axis and the volume percentage of the constituents boiling up to 100 C., determined according to the A. S. T. M. method, on the horizontal axis.

Considering e. g. the line P, the meaning of a point-situated on this line-which has a volatility is that a gasoline fraction corresponding to this point contains 85% of products distilling below C.

If therefore 100 c. c. of a gasoline with a nal boiling point of 200 C. is distilled in an A. S. T. M. apparatus 'up to the moment that the thermometer designates 100 C. the total distillate present in the receiver has a volatility :100. Assuming this quantity to be 30 c. c., upon the distillation then being continued up to say C. and the total distillate being at this moment tested again there may be present in the receiver 80 c. c. Of the total distillate (80 c. c.) 30 c. c. boil below 100 C., i. e.

therefore the Volatility of the total distillate equal about 37% In all three cases the said curve shows a break, the place of which dilers for every oil. In the graph it is indicated at every break to what (nal) boiling point-determined according to the A. S. T. M. method--it corresponds. Now the process according to the invention consists in the distillation of the gasoline-containing hydrocarbon mixtures, the I-I. U. C.-volatility curve of which shows a break, being effected in such a manner that a gasoline is obtained having a volatility and a final boiling point approximately corresponding to that where the break occurs.

According to my invention-in connection with what has been stated above with regard to the iniiuence of an insufficiently sharp fractinationthe distillation or fractionation preferably will have to be carried out in such a manner that a sharp separation between the desired gasoline and the higher boiling fraction is obtained. Accordingi. to my invention this separation can be effected so sharply that the boiling ranges of the two fractions-determined according to the A. S. T. M. method-do not overlap, and preferably even so sharply that the initial boiling point of the higher fraction lies at a temperature exceeding the iinal boiling point of the lower fraction say by 15 C. or more. Naturally this gap in the boiling range of the combined fractions does not really exist and is only due to the A. S. T. M. method not giving a complete 2 picture of the actual course of distillation of the individual fractions.

A sharp fractionation can be obtained by providing `for a goed contact between vapour and reflux in the distillation columns and the largest possible quantity of reflux.

Such fractionation ensures the largest possible yield of gasoline with a high H. U. C., that is te say this yield is not adversely influenced by the passing of constituents belong-v ing in the gasoline to the next higher fraction owing to an insuiicient fractionation. On the other hand the sharp fractionation tends to preclude that constituents belonging to the higher boiling fractions pass into the gasoline and thus unnecessarily decrease the H. U. C. thereof.

Obviously the location of the break in the H. U. C. volatility curve has to be previously determined experimentally for each hydrocarbon mixture to be distilled. 1n those cases where e. g. a special crude cil is worked in a distillation plant it is, oi' course, suicient to determine the situation or" the break only once-assuming that the composition of the crude oil is not modiiied appreciably-and to arrange the distillation accordingly.

Although it has appeared that many crude oils or gasoline-containing distillates of the most varying origin obtained therefrom show a H. U. C.-volatility line such as those depicted in the graph, the two parts of the line may, particularly in the case or" high aromatic oils, show a less gradual slope and tend to show peaks. The typical break, however, also occurs in that case.

Thus when distilling a hydrocarbon mixture of the composition a (see the graph) a gasoline will be obtained having a volatility of about 30 or with the corresponding final boiling point of about 168 C.

With the oil indicated by J the nal boiling point of the gasoline must be about 149 C., with the oil P about 135 C.

The higher fractions can be marketed as obtained, or may be used as motor gasoline, if desired, with the addition of suitable more Volatile materials and/or of some known anti-knock agents.

It is also possible to crack the higher -traction in order to improve the volatility and the H. U. C., and the product thus obtained can be brought on the market either as such, or mixed with other fractions, e. g. the lower fraction, as motor gasolines.

The value or" the process according to the invention is very evident when it is borne in mind that hitherto it has in fact always been the custom to determine the final boiling point of the gasoline arbitrarily and entirely independently of the nature of the crude oil. However, according to the invention the nal boiling point of the gasoline is determined designedly, which yields the above-mentioned advantages.

I claim as my invention: 1

1. In the process of manufacturing a straightrun gasoline having a relatively high anti-knock rating from a mineral oil containing gasoline components, boiling below 109 C. the steps or" distilling a sample of the oil, determining at relatively close intervals the values of the highest useful compression ratio of the accumulating distillate, forming a curve by plotting these values against the corresponding values of the volatility of the distillate expressed as thereof distilled at 109 C., locating on said curve a break occurring in its slope and corresponding to the critical :l

point after which the highest useful compression ratio begins to decrease at a relatively rapid rate for any subsequent decrease of volatility, and then subjecting said mineral oil to fractional distillation to separate therefrom a gasoline-type distillate having a volatility approximately corresponding to said critical peint.

2. In the process of claim i regulating the reliux ratio and the amount of reflux during the distillation of the mineral oil in such manner that the A. S. T. M. final boiling point of the gasoline-type distiilate lies below the A. S. T. M. boiling point oi the next heavier fraction.

JOHANNES HENDRIK WILLEB/I ROST VAN TONNINGEN. 

